Low water-loss cement slurry



.[UO'UZ Patented Nov. 25, 1952 bHUDD KLK'LKLNUL LOW WATER-LOSS CEMENTSLURRY Peggy J. Lea, Kansas City, Mo., and Henry B. Fisher,Bartlesville, Okla., assignors to Phillips Petroleum Company, acorporation of Delaware No Drawing. Application July 11, 1949, SerialNo. 104,153

Claims. (o 166-22) may not contain the usual minor ad itives common tohydraulic cements such as cal ium sulfate and/or calcium chloride as amamounts up 0 re ard the time of set, a

small but effective amount of inulin, and sufficient water to make aslurry.

In tfim of cementing oil wells and in grouting cracks in masonrystructures there is a tendency for the cement slurry to lose water atsuch an extent that it becomes dehydrated, set, or cracked prematurely,with the result that it cannot be properly placed in position due to anincrease in viscosity of the slurry, and resulting increases in forcenecessary to pump or move the slurry into position. This deleteriousdehydration is increased in many oil wells by the modern practice ofscratching, or scraping the drilling mud from the wall of the well bymechanical means prior to placing the cement, which often exposes porousformations which will absorb the water from the slurry. This isparticularly important when oil sands are penetrated, as artificialcontamination of oil sands with water will often cause shaley impuritiesin the sand to swell and reduce the permeability of said oil sand to avery great extent. Therefore water lost from the slurry tends to sealoff the formation to 011 fly. When it is intended to cement with slurry,and then gun perforate the hardened slurry, the gun perforator may notbe able to penetrate into the formation beyond the slurry to asuflicient depth to penetrate into the region beyond that in which theshaley impurities are swollen by the water extracted by the formationfrom the slurry. In such cases the oil production rate of the well maybe severely reduced by water contamination from the slurry.

We have found that by ad in d g a sma.ll hm'- ggegtiye amount 1 inglm inthe amount of 1%. based on the weight 0 ry cement and preferably usingordinary commercial Portland cement containing the usual additives,along with suflicient water to make a slurry, that the water loss asdetermined by filtration tests is greatly reduced and contamination ofthe formation is substantially prevented.

One object of the present invention is to provide an improved lowwater-loss cement slurry useful in grouting in general, in cementing thewalls of wells, and for cementing pipe in wells.

Another object is to provide a low water-loss cement which will notcontaminate the earth formations in bore holes with water to anysubstantial extent.

Another object is to provide a cement slurry suitable for use in oilwell cementing operations.

Numerous other objects and advantages will be apparent upon reading theaccompanying specification and claims.

In preparing the slurry the dry ingredients comprising hydraulic cement,with or without additives for increasing the time of set, the inertfiller material, such as sand or crushed limestone, and the inulin, maybe mixed together and later mixed with water, or any of them may bemixed separately with hot or cold water, and then mixed together to formthe cement slurry, as long as the mixing of the hydraulic cement withwater is done promptly before placing the slurry in position.

By h draulic cement we intend to include all mixtures of lime, silica,and alumina, or of Jim; and magnesia, silica, and alumina and iron oxide(magnesia for example may replace par 0 e lime, and iron oxide a part ofthe alumina) as are commonly known as hydraulic cements. Hy-

and ortlan uzza an cemen nclude s ag cemen s made from slaked lime andgranulated blast furnace slag. Because of its superior strength Portlandcement is preferred among the hydraulic cements, but as the art ofcements recognizes hydraulic cements as a dellnite class, and as resultsof value may be obtained with any member of that class, it is desired toclaim all hydraulic cements.

In most oil well cementing and grouting operations it is generallydesirable to use neat cement for added strength, but obviously it isalways possible to add any desired amount of an inert granular fillingmaterial or aggregate such as sand, ground limestone, or any of theother well wn inert were", as long as the amount added does not reducethe strength below the desired value. In operations in open wells it isoften desirable to use neat cement, because inert filling material willautomatically become detached from the walls of the well, and will tendto mix with and dilute the slurry to such an extent that it isundesirable to add any filling material to the slurry being forced intothe well.

The amount of wate added is not critical, it being obvious thatsuflicient water should be added to form a pumpable slurry, and thatwhen the slurry becomes pumpable no further water draulic cementsinclude h draulic limes, gra ier ements puzzalan cements naturalcement's',

cemen s.

need be added. One advantage of the slurry of the present invention isthat it is a low waterloss slurry, and therefore it is not necessary toadd excess water over the amount making the slurry pumpable as a reservefor expected losses, which would tend to reduce the strength of thecement.

In order to reduce the water loss of the cement slurry we add a smallbut effective amount of inulin.

mis also called alantin alant starch, $212 w menyanthin, or HaBl'In, andconsists of a white, ygroscopic, starch-like carbohydrate the formula ofwhich is possib 1o 5 z w ere C is carbon, H hydrogen, 0 oxygen an a: isan integer of the order of about 100. It melts and decomposes about 160C.

n rce are dahlias, Jerusalem artichokes, c ckori dandelions, burdockroots, golden rod roots and camas roots. Its prior art use is mainlymaking diabetic bread. The inulin used was chemically pure inulinpurchased from the Tennessee Eastman 00., but obviously commercialgrades will give valuble or equivalent results in cement slurries.

We have found that from 0.1% to 3% of inulin is particularly effectivein reducing the water loss of hydraulic cement aqueous slurries, withoutor with inert filling material present.

Afgrtland cement slurry was made up with fifteen fiFfind'sYiFcment tothe gallon of slurry. and 1% of inulin by weight (based on the dryPortland cement) was added to one-half of the sample. The two halves ofthe sample were tested separately according to the test procedure fordrilling muds described in A. P. I. code 29 and the sample which had noadditive lost 105 cc. of water in one minute and seconds through thestandard filter paper at -100 p. s. 1., whereas under the exact sameconditions the half of the sample containing the inulin only lost 110cc. of water in 11 minutes, seconds. Obviously, the portion of thesample without the additive would lose water to the formation of a wellto such an extent that it would dehydrate and have a premature setting,or bridging effect, which would increase the pressure needed to placethe slurry to a degree making the operation inoperative in many wellshaving porous formations, and the water from the slurry wouldcontaminate such formations, whereas the portion of the samplecontaining the additive would not readily give up water to such aformation, and would remain easily pumpable into place during the usualperiod of exposure to such a formation. 7

The cement slurry used in these tests was composed of 53 grams of 351E53 per 100 grams of cement to give a cement slurry containingapproximately 15 pounds of cement per gallon. The cement slurry set intoa hard cement suitable for use in well cementing and grouting after thewater-loss test described above when it contained the effective amountof water-loss reducing additive, but the same cement slurry without theadditive set in acracked and weakened condition after said abovementioned water-loss test due to water lost in said test.

It is also obvious that inert filling material will not substantiallyaffect the result of this test,

when used in an amount not large enough to deleteriously reduce thestrength of the cement slurry after setting.

The above example and tests are given for illustrative purposes andshould not be regarded as limiting the invention, the scope of which isset forth inthe following claims.

Having described our invention, we claim:

1. A cement capable of forming a fluid slurry when mixed with water,said cement comprising a hydraulic cement mixed with from 0.1% to 3% byweight of dry cement of inulin.

2. A cement capable of forming a fluid slurry when mixed with water,said cement comprising Portland cement mixed with from 0.1% to 3% byweight of dry cement of inulin.

3. A hydraulic cement slurry comprising a hydraulic cement, water, andfrom 0.1% to 3% by weight of dry cement of inulin.

4. A hydraulic cement slurry comprising Portland cement, water, and from0.1% to 3% by weight of dry cement of inulin.

5. The process of cementing a well which extends into a porous formationwhich comprises placing -a hydraulic cement aqueous slurry having areduced water loss adjacent to said porous formation by admixing withhydraulic cement from 0.1 per cent to 3 per cent by weight of the drycement of inulin, interacting therewith sufficient water to produce afluid slurry and introducing said slurry into said well into contactwith said porous formation.

PEGGY J. LEA. .HENRY B. FISHER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS OTHER REFERENCES Armstrong, "The Carbohydrates andthe Glucosides, pages 168, 169 (1924) Mackenzie. The Sugars and Their:Simple Derivativesfpages 180,181'(1931).

5. THE PROCESS OF CEMENTING A WELL WHICH EXTENDS INTO A POROUS FORMATIONWHICH COMPRISES PLACING A HYDRAULIC CEMENT AQUEOUS SLURRY HAVING AREDUCED WATER LOSS ADJACENT TO SAID POROUS FORMATION BY ADMIXING WITHHYDRAULIC CEMENT FROM 0.1 PER CENT TO 3 PER CENT BY WEIGHT OF THE DRYCEMENT OF INULIN, INTERACTING THEREWITH SUFFICIENT WATER TO PRODUCE AFLUID SLURRY AND INTRODUCING SAID SLURRY INTO SAID WELL INTO CONTACTWITH SAID POROUS FORMATION.